docs: scope advanced (audio-driven) DualSense haptics — NO-GO for now

4-agent feasibility read converged on three independent walls, any one fatal:
- host capture needs a kernel rebuild (CONFIG_USB_DUMMY_HCD off → no UDC for an
  f_uac2 composite gadget; everything else for the gadget IS present);
- near-zero Linux supply (only ~5-10 Proton titles via custom Wine patches emit
  it; hid-playstation/Steam-Input/RPCS3 don't);
- Apple client can't faithfully replay PCM haptics (CoreHaptics is discrete
  pattern-based; no public CoreAudio channel-3/4 routing).

Advanced haptics ride the DualSense USB *audio* interface, not HID, so the UHID
backend structurally can't carry them. Defer; the reachable 80% ("real DualSense
feel") is adaptive triggers over the HID 0x02 path we already parse + two-motor
rumble. New docs/dualsense-haptics.md records the walls + conditions for a future
go; roadmap §5 updated (HID DualSense backend built & live-validated).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/roadmap.md

@@ -77,13 +77,25 @@ select = a `pw_stream` with `Direction::Output` + `media.class=Audio/Source`.
   server creates **no touchscreen device** (headless KWin) — so touch currently no-ops on KWin
   (now logged once). The code is correct; it needs a backend that exposes `ei_touchscreen`
   (gamescope / newer KWin / the real iPad client path) to land. wlroots: no virtual-touch wired.
-- **Rich DualSense (XL, committed):** uinput can't carry HID output reports. Use **UHID** +
-  the kernel `hid-playstation` driver (the inputtino/Wolf approach): present a genuine
-  DualSense (real report descriptor, vendor 054C/0CE6, BT mode + CRC32) so games drive LED +
-  adaptive triggers + touchpad + gyro; forward `UHID_OUTPUT` (LED color, trigger effects) to
-  the client's `GCDualSense*` APIs. Needs a variable-length gamepad/touch event family
-  (the fixed 18-byte InputEvent can't hold touchpad/motion), per-client controller-type
-  negotiation, and a `/dev/uhid` udev rule. Phase after touch + a protocol-growth step.
+- **Rich DualSense — HID backend built & validated live.** `inject/dualsense.rs`: a hand-rolled
+  `/dev/uhid` codec (no bindgen) presenting a genuine USB DualSense (vendor 054C/0CE6, the 232-byte
+  inputtino report descriptor) bound by the kernel `hid-playstation` driver. The mandatory
+  GET_REPORT feature handshake (calibration 0x05 / pairing 0x09 / firmware 0x20) is answered, so the
+  kernel creates the full device (gamepad/motion/touchpad/lightbar). Input report `0x01` is built
+  from gamepad frames; output report `0x02` is parsed for LED RGB, player LEDs, and **adaptive
+  trigger effects (L2/R2)**. Protocol carries new side-planes: rich-input `0xCC`
+  (touchpad/motion) + HID-output `0xCD` (LED/triggers). `/dev/uhid` udev rule shipped.
+  *Remaining (paused, resume-able):* route gamepad frames → `DualSensePad` behind
+  `PUNKTFUNK_GAMEPAD=dualsense`, wire the `0xCC`/`0xCD` back-channel end-to-end (+ C ABI
+  `next_hidout`/`send_rich_input`), and render adaptive triggers + rumble on the Apple client.
+- **Advanced (audio-driven voice-coil) haptics — scoped, NO-GO for now (`docs/dualsense-haptics.md`).**
+  Driven by the DualSense's USB *audio* interface (4-ch, back 2 channels = haptic PCM), not HID — so
+  the UHID backend structurally can't carry it. Three independent walls: host capture needs a kernel
+  rebuild (`CONFIG_USB_DUMMY_HCD` is off → no UDC for an `f_uac2` gadget); **near-zero Linux supply**
+  (only ~5–10 Proton titles via custom Wine patches emit it; `hid-playstation`/Steam Input/RPCS3
+  don't); and the Apple client can't faithfully replay PCM haptics (CoreHaptics is discrete/pattern-
+  based, no public channel-3/4 routing). Deferred; revisit only if a real DS for capture + a UDC/host
+  path + a PCM-capable client all land. Adaptive triggers (HID, above) deliver the reachable 80%.
 
 ## 6. iOS/iPadOS → tvOS *(deferred)*